Influence of Particle Shape on Tortuosity of Non-Spherical Particle Packed Beds

: Tortuosity in packed beds or porous media is of significant interest in many fields, from geoscience to the chemical industry. Tortuosity plays a significant role in the mass transport in porous media, but also in their residual thermal or electric conductivity when the particles are not conducting. Several predictive models have been proposed to evaluate tortuosity, but there is still a gap when it comes to considering various particle shapes. The preponderance of tortuosity models substantiated in the literature are porosity-dependent while only a few include shape parameters. In this work, we propose a new model with sphericity and porosity to predict the tortuosity based on thermal simulations carried out with non-conducting particles for domains with no wall effect. The beds generated from rigid body simulations are compared and studied for different particle shapes with a sphericity range of 0.65–1. Sphericity showed a significant effect on the tortuosity compared with other 3D shape parameters (numbers of faces, edges, and vertices); therefore, only sphericity has been considered in the new model. The proposed new model is well suited for the porosity range of 0.3 to 0.4. In said ranges, it is an upgrade of the classical Zehner–Bauer–Schlünder (ZBS) model for the effective thermal conductivity of packed beds, with superior performance. DOI


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Particle Processes, a section of the journal Processes, is an interdisciplinary and international forum for the publication of high-quality original research, as well as of reviews, related to raw materials, intermediates, end-user products, and ancillary materials in particulate or granular form.The ability of particle systems is stressed to generate valuable properties through the combination of small (often nanoscale) building blocks to much larger functional units.The topics of interest include but are not limited to processes which create, transform, and upgrade particles, as well as processes that use particles and particle-based products in different sectors (chemicals, food, pharmaceuticals, advanced materials).Emphasis is put on sustainability and the green transformation of industry.From a fundamental point of view, advanced characterization techniques are addressed, as well as advanced simulation methods.All manuscripts submitted for publication under this Section will undergo the high-quality peer-review procedure of the journal Processes and, if accepted, will be rapidly published online.
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Influence of Particle Shape on Tortuosity of Non-Spherical Particle Packed Beds
Authors: Simson Julian Rodrigues, Nicole Vorhauer-Huget, Thomas Richter and Evangelos Tsotsas Abstract: Tortuosity in packed beds or porous media is of significant interest in many fields, from geoscience to the chemical industry.Tortuosity plays a significant role in the mass transport in porous media, but also in their residual thermal or electric conductivity when the particles are not conducting.Several predictive models have been proposed to evaluate tortuosity, but there is still a gap when it comes to considering various particle shapes.The preponderance of tortuosity models substantiated in the literature are porosity-dependent while only a few include shape parameters.In this work, we propose a new model with sphericity and porosity to predict the tortuosity based on thermal simulations carried out with non-conducting particles for domains with no wall effect.The beds generated from rigid body simulations are compared and studied for different particle shapes with a sphericity range of 0.65-1.Sphericity showed a significant effect on the tortuosity compared with other 3D shape parameters (numbers of faces, edges, and vertices); therefore, only sphericity has been considered in the new model.The proposed new model is well suited for the porosity range of 0.3 to 0.4.In said ranges, it is an upgrade of the classical Zehner-Bauer-Schlünder (ZBS) model for the effective thermal conductivity of packed beds, with superior performance.DOI:10.3390/pr10010167

Authors: Rezwana Rahman, Haiping Zhu and Aibing Yu
Abstract: Various simulations have been conducted to understand the macroscopic behavior of particles in the solid-gas flow in rotating drums in the past.In these studies, the no-slip wall boundary condition and fixed restitution coefficient between particles were usually adopted.The paper presents a numerical study of the gas-solid flow in a rotating drum to understand the effect of the specularity coefficient and restitution coefficient on the hydrodynamic behavior of particles in the segregation process.The volume fraction, granular pressure, granular temperature and their relationships are examined in detail.The boundary conditions of the no-slip and specularity coefficient of 1 are compared.In the simulations, two different sizes of particles with the same density are considered and the Eulerian-Eulerian multiphase model and the kinetic theory of granular flow (KTGF) are used.The results reveal that the hydrodynamical behavior of the particles in the rotating drum is affected by the boundary condition and restitution coefficient.In particular, the increase of specularity coefficient can increase the active region depth, angle repose, granular pressure for both small and large particles and granular temperature for large particles.With increasing restitution coefficient, the angle of repose decreases and granular pressure and temperature increase at the same volume fraction for both small and large particles.

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